Roll forming

ABSTRACT

Sheet metal is formed over a mandrel as the sheet metal and the mandrel move past successive pressure applying rolls in order to form tapered or other non-uniform sections. Pressure is applied to the sheet metal by the upper rolls of a roll forming machine having sleeves of elastomeric material adapted to conform to the variations in the shapes of the sections. An elongate mandrel may be successively fed into the roll forming machine or, for continuous operation, the mandrel may be made into sections which are hinged together and which form a closed loop.

United States atent 1191 Brooks, in et a1.

1451 Sept. 4, 1973 1 1 ROLL FORMING [75] lnvcntors: Barlow W. Brooks, Jr., Louisville;

- John R. Davis, Shelbyville; James A.

Henry, Finchville, all of Ky.

[73] Assignee: Roll Forming Corporation,

Shelbyville, Ky.

22 Filed: May 11,1970

211 Appl. No.: 36,139

[52] U.S. Cl 72/181, 72/207, 72/192 [51] Int. Cl B21d 5/08 [58] Field of Search 72/179, 176, 181, 72/199, 207-209, 192; 18/9-11 [56] References Cited UNITED STATES PATENTS 2,397,608 4/1946 Johnson 72/245 X 3,535,903 10/1970 Abernathy et a1.. 72/181 1,804,661 5/1931 Wagner 72/192 X 3,415,095 12/1968 Bringewald 72 20'/ x 926,253 6/1900 Hyde 72/207 2,150,416 3/1939 Cairns 72/207 X 3,354,682 11/1967 Dupuy 72/192 X 1,816,594 7/1931 Ledwinka 72/207 X 3,051,214 8/1962 Rutten 72/181 3,480,251 11/1969 Pietrzak l8/D1G. 44

Primary Examiner-Milton S. Mehr Attorney-Dybvig and Dybvig [57] ABSTRACT Sheet metal is formed over a mandrel as the sheet metal and the mandrel move past successive pressure applying rolls in order to form tapered or other non-uniform sections. Pressure is applied to the sheet metal by the upper rolls of a roll forming machine having sleeves of elastomeric material adapted to conform to the variations in the shapes of the sections.

An elongate mandrel may be successively fed into th roll forming machine or, for continuous operation, the mandrel may be made into sections which are hinged together and which form a closed loop.

5 Claims, 12 Drawing Figures Patehted Sept. 4, 1973 3,756,057

2 Sheets-Sheet 1 INVENTORS BA RLOW W. BROOKS, JR.

JOHN R. DAV/5 JAMES A. HENRY ROLL FORMING BACKGROUND OF THE INVENTION This invention relates to a roll forming method and apparatus especially adapted to produce tapered sheet metal sections using continuous roll forming equipment.

Roll forming machines having a series of pairs of vertically aligned powered rolls are well known. Such machines are used to advantage in the mass production of elongate pieces having a uniform cross section. The pieces are formed from sheet metal, a strip of which is fed between a first pair of rollers and gently bent. The strip continues through successive pairs of rolls which are constructed to cause successively more extreme bending or forming of the metal strip. At the exit end of the roll forming machine, the formed pieces are severed from the strip.

Roll forming machines have been limited in their use to the forming of pieces having a uniform cross section throughout their length. The need exists, however, for forming elongate pieces having a tapered or otherwise non-uniform cross section. Typically, tapered pieces have been formed in a press brake. It has also been sug gested to form tapered pieces by placing a strip of sheet metal over a forming mandrel which is in a fixed position. The sheet metal is then formed by passing rollers thereover. These manufacturing processes are not entirely satisfactory because the total length of the piece being formed is limited by the length of available equipment and because the processes are not continuous.

SUMMARY OF THE INVENTION An object of this invention is to provide a method and apparatus for continuous forming of tapered sections or other pieces having a non-uniform cross section. A further object of this invention is to provide a method and apparatus for using conventional roll forming machinery to form tapered sections or the like.

In the embodiment of this invention, a tapered section is formed from sheet metal by constructing the upper rolls of a roll forming machine with elastomeric material such as polyurethane elastomers and passing a forming mandrel between the rolls with a strip of sheet material sandwiched between the mandrel and the elastomeric material. The elastomeric material has sufficient resiliency that it conforms to the tapered shape of the sheet material determined by the forming mandrel.

In another embodiment of this invention, the forming mandrel is constructed from a plurality of separate sections with adjacent sections hinged together into a closed loop. Means are provided on the bed of the roll forming machine for supporting the closed loop so that the mandrel continuously moves with the sheet material between the forming rolls.

Other objects and advantages will become apparent from the following description and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a sheet metal section manufactured in accordance with this invention;

FIG. 2 is a perspective view of a forming mandrel used in the manufacture of the section of FIG. 1;

FIG. 3 is a side elevational view of a roll forming machine modified in accordance with this invention to include a hinged forming mandrel and shows a coil of sheet material for use therewith;

FIG. 4 is a side elevational view of a portion of a roll forming machine in accordance with this invention;

FIG. 5 is a plan view, with housing parts removed, of the portion of the roll forming machine shown in FIG.

FIG. 6 is a cross sectional view of a pair of forming rolls with a strip of sheet material and a forming mandrel passing therebetween as viewed in the direction of arrows 6-6 of FIG. 4;

FIG. 7 is a perspective view of a portion of the hinged forming mandrel shown in FIG. 3;

FIG. 8 is a side elevational view of parts of two sections of the mandrel of FIG. 7;

FIG. 9 is a plan view of the underside of a portion of the mandrel of FIG. 7 as indicated by the arrows 9-9 thereof;

FIG. 10 is a view similar to FIG. 6 but showing a different embodiment;

FIG. 11 is a side elevational view of the embodiment of FIG. 10 taken along section line 11-11 thereof; and

FIG. 12 is a plan view of one pass of a roll forming machine provided with still another embodiment of roll forming apparatus in accordance with this invention.

DESCRIPTION OF TI-IETREFERRED EMBODIMENTS With reference to FIG. I, a roll formed piece or section made in accordance with this invention is generally designated 20. The section 20 has an inverted U- shaped, longitudinally extending midportion 22 and side flanges 24 and 26. The transverse cross section of the midportion 22 of the section 20 tapers from its leading end, designated 28, outwardly to its trailing end, designated 30. As will become more apparent, the section 20 is formed from a strip of sheet metal having a uniform width; hence the widths of the flanges 24 and 26 taper from a maximum at the leading end 28 to a minimum at the trailing end 30. The section 20 is typical of hat sections used, for example, in the construction of aircraft In the final assembly in which such sections are used, the flanges 24 and 26 may optionally be left on or removed. Sections such as the section 20 may be quite long, on the order of seventy feet or more. To date there has been no practicable process for forming very long tapered sections in one piece. This invention is directed primarily to the forming of elongate sections having tapered surfaces such as the midportion 22 of the section 20. Other elongate sections, such as those having undulating surface portions, may be made by the practice of this invention.

In accordance with this invention, a section such as the section 20 is manufactured using conventional roll forming machines modified to resiliently apply pressure to the sheet metal strip from which the section is made and the sheet metal is formed over a forming mandrel. Referring to FIG. 2, a forming mandrel which may be used in the manufacture of the section 20 is generally designated 32 and consists of a solid, elongate piece of metal or other substantially inelastic material having a base plate portion 34 and a longitudinally extending body portion 36. The shape of the body portion 36 corresponds to the hollow shape of the midportion 22 of the section 20. As apparent, the section 20 may be manufactured by deforming a flat strip of sheet metal into intimate contact with the top surface of the forming mandrel 32. For this purpose, the mandrel 32 must have sufficient strength and rigidity to withstand the pressures of the members used in forming the sheet metal thereover; it is preferably made from steel.

The constructional details of a roll forming machine are, for the most part, unimportant to this invention, it being understood that the method and apparatus to be described herein may be used with any commercially available roll forming machine. Briefly, one type of a roll forming machine is generally designated 40 in FIG. 3 and includes a machine bed 42 supporting a drive housing 44 from which project a plurality of spaced upper spindles 46 and spaced lower spindles 48 for an array of upper, forming or pressure applying rolls 50 and lower, back-up rolls 52, respectively. Each upper roll 50 is vertically aligned with a lower roll 52 and two such rolls together form a pass or station.

In conventional roll forming operations the lower roll serves as a back-up or abutment and the upper roll applies pressure to sheet material causing it to be deformed to conform to the shape of the two rolls. A strip of sheet material 54 having a uniform width is taken from a coil 56 mounted on a support 58 and fed to the first such pass. The pressure applied to the strip 54 is sufficient to cause it to be drawn by friction from the coil 56 and through all of the passes. Each succeeding pass further forms the sheet material, the working surfaces of the rolls 50 and 52 being developed with the proper configuration so that the strip 54 has the desired final shape after traversing all the passes. For purposes of illustration, only four passes of aligned rolls 50 and 52 are illustrated in the drawings. However, those familiar with the art will realize that there normally would be several additional passes used in most roll forming operations.

Usually, roll forming machines are operated continuously and a cutter mechanism (not shown) cuts the formed sections or pieces to the desired lengths. With reference to FIGS. 3 and S, the spindles 46 and 48 may all be driven at the same rotational speed by driving means'including a clutch 60 and a gear train 62 connected thereto. The spindles are supported by bearing blocks such as the designated 64 and devices known as outboard stands 66 in which the lower spindles 48 are journalled for rotation. The upper spindles 46 are journalled for rotation in sliding boxes 68 which are vertically movable in the outboard stands 66, the positions of which are controlled by adjusting screws 70. In FIG. 3, the right side outboard stand has been removed in order to show the rolls 50 and S2. The basic roll forming machine 40 illustrated herein is only exemplary of various types of roll forming equipment. Other roll forming machines have direct motor rather than gear drives. The locations of the pressure applying and back-up rolls may be opposite from that described above and-the rolls may be driven at different speeds along the length of the machines and some rolls not driven at all. Generally speaking, this invention may be used with any conventional roll forming machine.

Referring now to FIGS. 4, and 6, a roll forming machine in accordance with this invention is provided with a novel set of forming rolls adapted to receive the mandrel 32 as well as a strip of sheet material 54 and also adapted to resiliently apply pressure to cause the strip of sheet material 54 to be formed about the mandrel 32. To this end, the back-up rolls 52 are made from steel or other substantially inelastic, rigid material and formed with substantially cylindrical surfaces 72 for receiving and supporting the planar lower surface of the mandrel base portion 34. As shown in FIG. 6, the sides 74 of the backup rolls 52 may be formed with annular flanges for confining the sides of the mandrel base portion 34 therebetween.

In accordance with this invention, the forming rolls are formed primarily from contoured sleeves 76 of elastomeric material straddled by back-up plates 78. The sleeves 76 and back-up plates 78 are affixed to the spindles 46 in any conventional fashion such as by keys (not shown). Although a variety of elastomeric materials may be used in constructing the sleeves 76, the material known as a polyurethane elastomer is preferred. Such material is commonly used for pressure pads in press dies. The material should have a high durometer, on the order of or more, and usually 85 or higher. Polyurethane elastomer material of high durometer has a sufficient resiliency that an unstressed, two inch thick piece may be compressed to one inch. Upon removal of pressure, the material will return substantially to its original shape.

In FIG. 5, the elastomeric sleeve of the roll 50 for the first pass is designated by the reference character 76 and the elastomeric sleeves of the second, third and fourth passes are designated 76a, 76b and 76c, respectively. The outer, working surface of all of the sleeves are surfaces of revolution. The working surface of the first pass sleeve 76, when unstressed, is cylindrical. The center of the sleeve 76a is cut away to define a shallow groove bounded by sloping end walls 80 and 82. The sleeve 76b of the third pass is similarly formed but with a deeper groove, whereas the sleeve 760 has astill deeper groove bounded by substantially planar end walls 84 and 86. The grooves in the sleeves 76a, 76b and 760, when unstressed, are substantially as wide as the narrowest, leading end of the mandrel body 36.

In operation, the rolls 50 and 52 are rotated as described above and the mandrel 32 is fed therebetween in alignment with the sheet metal strip 54. The mandrel 32 and the strip 54 are frictionally driven from one pass to the next by the rolls 50 and 52, as in ordinary roll forming processes. The elastomeric sleeves 76, 76a, 76b and 76c have a sufiiciently high durometer to bend or deform the moving sheet metal strip 54 over the mandrel 32 traveling therewith. Even though cylindrical, the first pass sleeve 76 starts the forming of the metal sheet 54 over the body portion 36 of the forming mandrel 32 because it is spaced from its associated back-up roll 52 by a spacing less than the thickness of the mandrel 32 and the sheet strip 54. The working surfaces of the sleeves 76a, 76b and 760 are likewise placed sufficiently close to their associated back-up rolls 52 that the metal strip 54 is further formed about the mandrel 32 as the strip 54 and mandrel 32 move therepast. Because of their more extreme working surfaces, the sleeves 76a, 76b and 76c further form the metal sheet 54 over the mandrel 32, progressively causing greater surface contact between the sheet 54 and the mandrel 32. The final forming of the sheet material 54 over the mandrel 32 by the sleeve 76c may be sufficient to bring the entire lower surface of the sheet material 54 into intimate engagement with the top surface of the mandrel 32.

Sheet metal normally has some memory and it may be advisable or necessary to further draw the strip 54 into engagement with the mandrel 32. For this purpose a side stand" including a pair ol generally conical forming members 88 and 90 is shown located just beyond the forming member 76c. The forming members 88 and 90 are supported in straddling relation to the body portion of the mandrel 32 by a fork-like support 96 mounted on the spindle 48 of the back-up roll 52 therebeneath. Journalled in the top of the support 96 are spindles 98 by which the forming members 88 and 90 are rotatably mounted about vertical axes. The side stand members 88 and 90 are usually not driven but are caused to rotate by their frictional engagement with the moving sheet metal strip 54. Side stands are commonly used in roll forming machines, the side stand illustrated in FIGS. 4 and 5 differing from conventional ones only in that the forming members 88 and 90 are made of elastomeric material rather than metal.

With continued reference to FIGS. 4, 5 and 6, because the separation between the working surface of the sleeve 76 and the cooperating back-up roll 52 is less than the height of the mandrel 32, the lowermost center portion of the sleeve 76 is compressed to conform to the planar top configuration of the mandrel 32. It will also be apparent that, as the mandrel 32 progresses through the passes, the succeeding sleeves 76a, 76b and 760 as well as the side stand rolls 88 and 90 will be compressed to conform to the increasingly wider sections of the mandrel 32. Accordingly, the end walls, such as those designated 80 and 82, of the grooves in the sleeves 76a, 76b and 760, as well as the confronting surfaces of the side stand members 88 and 90, will be gradually spread apart by the wider portions of the mandrel body 36 as it moves therepast.

Polyurethane and other types of elastomeric material of high durometer can be machined to configurations such as those shown in FIG. 5. In machining the elastomeric sleeves, they are shaped to cause the metal strip to be formed about the narrowest portion of a tapered mandrel, taking into account, of course, the thickness of the sheet metal strip to be formed. Preferably, the elastomeric material is capable of compressing or stretching sufficiently to conform to the mandrel along its entire length. It will be appreciated that the shapes of the sleeves illustrated are designed for use in forming the section 20. Other pieces or sections would require the use of elastomeric sleeves having different shapes. As conventional in the roll forming art, side stands would be located where desirable. For example, side stands may also be located between pairs of pressure applying rolls.

Occasionally the desired taper of a section or roll formed piece to be manufactured is so great that the elastomeric sleeves will not compress sufficiently to accommodate the entire length of the mandrel. Accordingly, it may be desirable to build an additional resiliency into one or more of the forming rolls. With reference to FIG. 12, a forming roll having a greater resiliency than that provided by an elastomeric sleeve 76 is illustrated. In FIG. 12 the forming roll has been split into two elastomen'c sleeves 100 and 102, both of which are mounted for sliding movement upon a spindle 104 journalled in bearings located in bearing housings 106 and 108. The sleeves 100 and 102 are biased toward one another by springs 110 and 112, respectively, coiled about the spindle 104 and confined between the adjacent bearing housings and the side faces of the sleeves. As apparent, the sleeves 100 and 102 will be forced outwardly away from one another toward their adjacent hearing housings I06 and 108, respectively, as the wider sections of the tapered portion of the mandrel, designated 114, pass therealong. Such construction obviously will result in the forming of a strip of sheet material, designated 116, at least partially over the mandrel 114.

As mentioned above, the construction shown in FIG. 12 is intended to provide greater resiliency in the pressure applying rolls than could be obtained without the springs and 112. Under some circumstances, however, it may be preferred to use the springs 110 and 112 with split solid rolls, such as steel rolls, the springs themselves providing sufficient resiliency to accommodate changes in the cross sectional dimensions of the mandrel.

An entirely conventional roll forming machine can be used with the rolls having elastomeric sleeves by feeding the strip material, such as that designated 54 and 116, to the machine in the usual manner. At the same time, elongate mandrels such as the mandrel 32 are fed in longitudinal alignment with the strip material into the machine. The mandrel, of course, must be removed as it exits from the machine when the roll forming operation is complete. It is preferred, however, to automatically and continuously feed a mandrel to the forming rolls. For this purpose, the mandrel is preferably divided into sections hinged together and forming a closed loop.

Referring to FIGS. 3 and 7 9, the preferred construction of a mandrel is generally designated 118 and consists of a continuous loop of mandrel sections, designated 120, connected together along their lower edges by "hidden" hinges 122, the exposed parts of which are flush or coplanar with the lower surfaces of the mandrel sections 120. The sections 120 are so formed that the adjacent ends of adjacent sections 120, when aligned in a horizontal plane, are in abutment across their entire surfaces. Accordingly, the parts of the mandrel 118 feeding through the passes formed by the forming and back-up rolls provide an unbroken upper surface over which the sheet material is formed. Suitable guide means, such as the guide rollers 124 shown in FIG. 3, are preferably mounted at each end of the machine to guide the mandrel to and from the rolls. As an alternative to the hidden hinges illustrated, the hinges could extend beneath the lower surfaces of the mandrel and the back-up rolls could be notched to receive the depending hinge portions. It is only necessary that the hinges do not obstruct and are thus remote from the forming surface of the mandrel.

Depending upon the length of the sections to be manufactured, substantially the entire length of the mandrel 118 may be used in manufacturing a single piece, or it may be used in manufacturing several pieces. In FIG. 7 the mandrel section designated 120a is that mandrel section which would form the leading end 28 of the roll formed section 20 shown in FIG. 1, and the mandrel section designated 120b is that portion of the mandrel which is used in forming the trailing end 30 of the roll formed section 20. The mandrel section designated 120a in FIG. 7 serves the same function as the section 120a in forming the leading end of another roll formed section 20. Between the section 120b and 120C there is another mandrel section, designated 120d, having a taper opposite that from the taper of the mandrel sections 120a through 120b. The mandrel section 120d is an intermediate or transition section which provides for a gradual reforming of the metal strip between two roll formed sections. The transition section of sheet material between roll formed pieces would ordinarily be cut away and discarded. The transition section 120d is necessary to avoid crimping or deforming of the metal which would result from abrupt changes in transverse cross section. Depending upon the degree of taper, the reversely tapered transition sections may be longer or shorter than that illustrated in FIG. 7. Also the transition sections could be notched to accommodate the cutoff blade used to sever the formed sections from the strip of sheet material at the end of the roll forming operation.

As previously mentioned, resilient forming rolls may be used not only for sections which are gradually tapered from a narrow dimension to a wide dimension throughout their length, but they may also be used in forming pieces having an undulating surface. If the taper is so extreme that the pressure exerted on the mandrel by the rolls tends to cause the mandrel to move in a reverse direction to the movement of the sheet metal piece being formed, it may be desirable to positively drive the mandrel rather than rely on the frictional drive between the rolls and the mandrel. A positive drive is shown in FIGS. 10 and 11, wherein the back-up rolls designated 130 are provided with gear teeth 132 and the mandrel designated 134 has rack teeth 136 on its lower surface meshing with the gear teeth 132. As apparent, the mandrel 134 thus is positively driven by the rotatably driven back-up roll 130. Of course, the sheet metal strip 138 would not have to be driven because it is squeezed and frictionally driven by the elastomeric sleeve portion of the forming roll, designated 140. The gear and rack arrangement may be used with either a one-piece mandrel, such as the mandrel 32, or with a sectionalized mandrel, such as the mandrel 118.

Although the presently preferred embodiments of the invention have been described, it will be understood that various changes may be made within the scope of the appended claims.

Having thus described our invention, we claim:

1. In a process of roll forming a strip of sheet material into a shape having a non-planar cross section which varies along its length with the use of a roll forming machine having a plurality of passes comprising a back-up roll and a forming roll, and drive means for rotating at least some of said rolls to cause the sheet material therebetween to be continuously moved from one pass to the next pass, the improvement comprising the steps aligning the sheet material with surface portions of a mandrel having a non-planar cross section against which the sheet material can be formed to the desired shape, and exerting pressure against the mandrel and the sheet material at said passes with the use of contoured elastomeric sleeves forming part of said forming rolls which engage the side of the sheet material opposite the mandrel, said pressure being applied by spacing said forming rolls sufficiently close to said back-up rolls to cause said elastomeric sleeves to be pressed into engagement with the sheet material, the elastomeric sleeves being sufficiently stiff to form said sheet material and sufficiently resilient to accommodate variations in the shape of the cross section whereupon said sheet material is caused at least partially to conform to the surface portions of the mandrel with which it is engaged, said forming rolls being constructed to progressively form said sheet material into greater conformity to the surface portions of the mandrel as said mandrel and said sheet material move from pass to pass.

2. The improvement of claim 1 further including the step of positively driving said mandrel from pass to pass by providing cooperating gear teeth on said mandrel and said back-up rolls.

3. The improvement of claim 1 wherein said elastomeric sleeves are formed from a polyurethane elastomer.

4. The improvement of claim 1 wherein at least some of said forming rolls consist of two sections and further including the biasing of said two sections toward one another.

5. The improvement of claim 1 wherein said mandrel is divided into a plurality of separate sections, adjacent ones of said sections being hingedly connected together, and said mandrel is formed in a continuous loop, said process further including the steps of supporting and guiding said loop for continuous movement in one direction along said passes.

UNITED STATES PATENT OFFICE CETIFICATE 0F CORRECTION PATENT NO. 3,756,057

DATED September 1973 INVENTOR(S) I Barlow W. Brooks Jr. et al 1t is-certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line tl "the" should be ---an--. Column 2, line +2, insert a period after "aircraft". Column 8, line 5, insert "of" after "steps".

Signed and Scaled this sixteenth D ay Of September 1975 [SEAL] A trees I.

RUTH C. MASON C. MARSHALL DANN Alresting Officer (mnmissiuner of Patents and Trademarks 

1. In a process of roll forming a strip of sheet material into a shape having a non-planar cross section which varies along its length with the use of a roll forming machine having a plurality of passes comprising a back-up roll and a forming roll, and drive means for rotating at least some of said rolls to cause the sheet material therebetween to be continuously moved from one pass to the next pass, the improvement comprising the steps aligning the sheet material with surface portions of a mandrel having a nonplanar cross section against which the sheet material can be formed to the desired shape, and exerting pressure against the mandrel and the sheet material at said passes with the use of contoured elastomeric sleeves forming part of said forming rolls which engage the side of the sheet material opposite the mandrel, said pressure being applied by spacing said forming rolls sufficiently close to said back-up rolls to cause said elastomeric sleeves to be pressed into engagement with the sheet material, the elastomeric sleeves being sufficiently stiff to form said sheet material and sufficiently resilient to accommodate variations in the shape of the cross section whereupon said sheet material is caused at least partially to conform to the surface portions of the mandrel with which it is engaged, said forming rolls being constructed to progressively form said sheet material into greater conformity to the surface portions of the mandrel as said mandrel and said sheet material move from pass to pass.
 2. The improvement of claim 1 further including the step of positively driving said mandrel from pass to pass by providing cooperating gear teeth on said mandrel and said back-up rolls.
 3. The improvement of claim 1 wherein said elastomeric sleeves are formed from a polyurethane elastomer.
 4. The improvement of claim 1 wherein at least some of said forming rolls consist of two sections and further including the biasing of said two sections toward one another.
 5. The improvement of claim 1 wherein said mandrel is divided into a plurality of separate sections, adjacent ones of said sections being hingedly connected together, and said mandrel is formed in a continuous loop, said process further including the steps of supporting and guiding said loop for continuous movement in one direction along said passes. 